1. Field of the Invention
This invention relates to a crane having a boom with multi-section, bolted connections and, more specifically, to such connections for crane boom parts having a lattice structure.
2. Description of the Prior Art
There have heretofore been numerous types of cranes having multi-section booms in which the sections are connected to provide the overall assembly of the boom.
Bolted connections, such as those disclosed in German Patent No. 37 06 301, have heretofore been used, among other things, to connect boom joints which are, in particular, the joints of lattice boom parts. They may include so-called bolt joints which are welded onto the boom tubes. The connections are generally three-piece configurations and include a fork, a strap and a bolt.
During the assembly of the boom parts or joints, initially, all the fork-shaped parts must be placed in contact with the corresponding strap with their respective holes in alignment. A bolt or pin member is then inserted or hammered into the aligned holes. At each connection point or location, there are four of these three-piece connections with two of them being in the upper flange and two of them being in the lower flange.
It has been found that manual assembly of these types of connections is very time-consuming. It is particularly noteworthy that, because of the considerable weight of the boom parts, it is quite difficult to bring the holes into alignment for the insertion of the bolts or pin members. In particular, the fourth or last bolt can frequently only be inserted or hammered in with a great deal of force. To some extent, this occurs because of the manufacturing and assembly tolerances for the forks and straps and for the parts to be connected, such as the boom joints. However, it also occurs because, in the vertical longitudinal plane of the boom, there are two degrees of freedom of movement for the joints during assembly. Only the fastening or bolt extends in a transverse direction relative to the longitudinal axis of the boom. Because of the shape of the fork and the strap, the fastening or bolt must be introduced into the "eyelet" of the fork-shaped piece. In the vertical longitudinal plane of the boom, the aligned position for receipt of the fastening or bolt must be achieved manually.
Moreover, the bolts in the upper flange plane can generally be reached only by means of an elevator or the like, which further increases the expense of the assembly process.
Other such multi-section booms for cranes, shovels or the like are disclosed in U.S. Pat. Nos. 3,323,660; 3,511,388; 4,316,548; 4,358,021; 4,601,402; and 4,711,358. These booms are extremely long, to extend as much as several hundred feet, and have transverse widths, which are perpendicular to the length, which may be several stories high when the booms are disposed to extend generally horizontally.